Dead-front underground primary distribution systems are practical, largely because of the widespread use of separable insulated loadbreak connectors by which high voltage cable may be connected to electrical equipment such as transformers. An important part of the separable loadbreak connector system is a loadbreak bushing. A typical loadbreak bushing comprises an insulating housing having an axially extending bore which is closed at one end by a terminal contact, the latter being adapted for connection to a high voltage terminal of an electrical equipment. A snuffer/contact assembly is supported within the bore for axial movement therealong, the assembly comprising a bore contact with an insulating sleeve extending therefrom. The sleeve contains an ablative material which, if the lineman attempts to connect a cable terminator under a fault condition, responds to prestrike arcing by generating an arc extinguishing gas within the sleeve. The effect of the gas generated is to extinguish the arc and also, in the case of a gas-actuated loadbreak bushing, to displace the snuffer/contact assembly along the bore. The snuffer/contact assembly is constructed as a composite piston and is displaced by the gas pressure from a first, seated position to a second position at which it makes contact with the cable by a loadbreak elbow.
In the past, loadbreak bushings were of rugged construction capable of withstanding numerous fault closures. Modern designs cannot safely withstand repeated fault closures, however, and present a serious hazard to a lineman who attempts to perform a subsequent fault closure.